I have Ubuntu 12.04 as host and Win7 as guest. I installed VirtualBox 4.1 and Extension Pack 4.1 from Oracle website. I also enabled USB 2.0 from Settings of my VM. My Win7 VM doesn't regconize USB (Flash Drive and Kindle Fire).
How to fix it?

Update: I added my current user to vbusers group but it doesn't work as well.

4 Answers
4

You also need to set USB filters so that the USB devices get sent to the guest OS.

From the main Virtualbox window open the Settings dialog, then the USB section, then click the little "add filter" button on the right side of the screen. You should be able to create a filter from any currently connected USB devices.

After you've done this (maybe restart to be sure the host OS isn't capturing any of the USB devices for itself--Ubuntu will try to automount the flash drive so you might also want to check and make sure that it is unmounted too) then boot into the guest OS and you should see your USB devices.

Good luck.

Edit: note on USB filters

It's my understanding that a device being used by a guest OS with a USB filter will not be accessible by the host OS while the guest OS is running. Therefore, one should choose carefully what usb devices to create filters for.

You should create USB filters for things that you plan on only using with the guest OS (often peripherals that don't work with the host OS and will only work with the guest OS) and when you won't require being able to access the device from the host OS while the guest OS is running. For example I have a USB banking dongle from my bank, ICBC, that is not compatible with Linux so I use a virtualized installation of Windows XP for banking and use a USB filter to grab the USB dongle.

Examples of good devices to create filters for:

USB banking dongles that only work with guest OS

e-readers (Kindle,Nook,etc.) that you plan on using only (or primarily) with the guest OS.

external soundcards that only work with the guest OS or require the guest OS for full functionality

Examples of bad devices to create filters for:

USB input devices (mouses or keyboards) that you would like to use with the host and guest OSes. Virtualbox will allow the guest OS access to these devices by default so there is no need for the guest OS to directly control them (well, I could think of some specialized reasons but I will digress...).

USB storage devices that you want the guest and the host OSes to both be able to access at the same time. Instead, mount the drive on the host OS and use shared folders to share the drive to the guest OS.

I added my something to USB tab as you said but the keyboard of my PC doesn't work. The mouse can't move out of the guest machine.
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Emerald214May 21 '12 at 6:15

@Emerald214: this indicates that Guest Additions are not yet installed in the guest Windows7.
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TakkatMay 21 '12 at 6:30

No, I've installed and used it before I installed Extension Pack. I think this is a bug. Really don't want to reinstall this VM.
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Emerald214May 21 '12 at 6:31

@Emerald214: I'm not quite clear what problem it is you are having, is it your keyboard that isn't working, your mouse, or both? Are they only working in the host OS or only working in the guest OS? If you use a USB mouse/keyboard and added a filter for either one, then that could make the USB mouse/keyboard no longer work on the host OS. So I would recommend not adding filters for a USB mouse or keyboard...
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adempewolffMay 21 '12 at 8:45

1

@Emerald214: also, I'm not sure if this is your problem, but make sure to use the host key (usually the right ctrl key) to uncapture the keyboard and mouse so the host OS can use it again. Once guest additions have been installed you can also enable mouse integration (host + I, or from the machine menu) so you don't have to capture and uncapture the mouse anymore.
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adempewolffMay 21 '12 at 8:51

I had the same problem and fixed it by clicking in the VirtualBox group of my user. You can access it installing gnome-system-tools (it does not come with Ubuntu 12.04 Precise Pangolin), either via the Ubuntu Software Center, Synaptic or by typing in the terminal:

sudo apt-get install gnome-system-tools

Remember that to paste in the terminal you have to use CTRL+SHIFT+V, as opposed to CTRL+V

You will probably have to enter your password to allow the installation and add a Y (as in yes) to finish installing the packages.

Then you head to your Dash home and type users. You will see two applications. The good one is Users and Groups.

You then have to click on Advanced settings for your user and enter your password.

Now you will be shown a window with three tabs. Click on User Privileges. Find the line that says Use Virtualbox virtualization solution and then OK.

You may be asked to enter your password again. Then click on Close and log-out and log-in again.

When you start VirtualBox you should see a whole bunch of new USB devices.